Planograph co



w. s. BLAUVELT.

SEMIMECHANICAL TELEPHONE SYSTEM.

lAPPLICATION FILED OCT I2, 1917.4

Patented July 22, 1919.

3 SHEETS-SHEET l A TTORNEYS.

THE COLUMBIA PLANoGRAPl-I C0., wsHlNuTDN, D. C

W. B'LAUVELT.

SEMIMECHANICAL TELEPHONE SYSTEM. APPLICATIONA FILED ocr. 12.-'1'911f 1,310,780. Patented July 22,1919.

3 SHEETS-SHEET 2- Card 2 Cordfsa 4 .H05 to 7 III;

' INVENTOR.

ffy W6. Zauvjl u I Q ATTORNEYS.

COLUMNA PLANculg/PH C0.. WASHINGTON. D. c.

W. G. LAUVELT.

SEMINIECHANICAL TELEPHONE SYSTEM.

APPLICATION FILED ocT. I2l 1911.

3 SHEETS-SHEET 3.

Canis/X04 Cards@ i0 42 56 Cards/:ma

Ill-m.l

IN VEN TOR.

WILLIAM Cr. BLAUVELT, OFNEW YORK, N. Y., AssICNOIe, tro` AMERICAN TELEPHONE f AND` TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

SEMIMECHANIQAL TELEPHONE srsrnM.

I Specication of Letters IElatent. `Patented July 22, 1919.

Application led October 12, 1917, Serial No. 196,281. p

To all whom t may concern: l

Be it known that I, WILLIAM Gr. BLAUVELT,

lresiding at 30S WV. 82nd street, New York city, in the county `ofNew York and State or' New York, haveinvented certain Improvements in Semnnechanioal Telephone Systems, of whichthe following is a speci- 1 lication.

This inventionrelates to semi-mechanical i telephone systems, and more particularly concerns the provision of means whereby when an operator answers a call by inserting the plug of an idle cord circuit into the jack of a calling subscriber, the operators talking set and associated apparatus will be automatically connected with that particular cord circuit.

It is one of the objects of this invention to provide means whereby the time necessary to effectV this operation maybe reduced to a minimum, the apparatus necessary to produce this result being greatly simpliiied.

In constructions heretofore used, where an operator has at her disposal a large number of cord circuits to each of 4which she mustbe able to connect her listening and controlling apparatus, in order to effect said connections in a minimum space of time, it has been proposed to arrange the cordcircuits in groups of some small number, with a selecting switch for each group to select a particular cord circuit in the group, and an additional selecting switch common to the groups for selecting a group and connecting the operators set to the terminals of -the group. Suppose, for instance, there are twenty-five Vcoid circuits, divided into groups of five cach. Five switches, preferably' of the sequence switch-type, shown for instance in U.4 S. patent to McBerty 1,105,811, -August 4, 1914, or U. Sl `patent to Reynolds', et al., 1,127,808, February 9, 1915, would be provided, each having a position for each cord circuit of thc group to which the switch is` assigned. An additional switch ofthe same type would .be provided, common to the other five, and having a position corresponding to each of the groups, and if desired, an additional position in which the operators set would be connected to no group. If a cord in any group is used in answering `a call, as soon as the operator plugs into the answering jack, the switch v `of that group begins to seek that particular `second or less, a bridge'is connected across the cord circuit and through the switches,

said bridge including the operators talking set, as well as ringing and coin return keys.

Inasmuch as the ringing and coin return keys are included in a bridge of the talking circuit, it is necessary with this arrangement to provide means to open the coi-d circuit to prevent the application of ringing vor coinA return current to the calling end of the cord. This was accomplished byY providing each cord circuit with arelay whose circuit was extended through the selectingV kswitches to the ringing and coin control keys, said relay functioning to open the cord circuit upon the operation of any key.

In accordance with the present invention lthe selecting switches are arranged so that the'cord `selecting switch, upon selecting a `cord circuit, introduces into that cord cir- Y`cuit a loop extendingto the group switch, which switch in turn, upon selecting the group, introduces in the first loop another loop in which. the coin control and ringing keys are serially included and across which the operators set is bridged. By this arrangement, when a cord circuit is selected the coin control and ringing keys are serially included therein so that the key itself when operated opens the cord circuit. This obviates the necessity for the relays individual to each cord and provides a more accurate operation `ofthe ringing and coin control apparatus, which bear the same relation to ,the cord circuit as in manual practice.`

The invention may be more fully understood by reference to the drawing in which Figures 1, 2 and 3, `when arranged so that Figs. 2 and 3 areend to end with Fig. 1 horizontally at the top oi Fig. 2,` constitute a circuit diagram ofthe arrangements of the invention. L

Referring to- Fig. 1, a cord circuit is shown terminating in plug P, and consistingof two sections, 1 and 2, the latter of which is associated by means of tlieusual induction coil-,with a circuit 3 leading lto automatic switching machinery of a wellknown type. As the switching machinery forms no part of the present invention it is not illustrated.

In order to control the sequence of operations whereby when the cord circuit is taken for use a sender is selected and the sending operations performed, a sequence switch 100 is provided, said sequence switch being of the type illustrated in the patents to Mc- Berty or Reynolds above referred to; A sending apparatus 4: is also illustrated, said sending apparatus being adapted to be associated with the cord circuit illustrated in Fig. 1, or any otherV cord circuit to which it has access, by means of a finder switch F. The sending apparatus has associated therewith a sequence switch 300 of the type already described for controlling its-operations. Similarly, the finder switch F has associated therewith a sequence switch 200 for a similar purpose. The contacts of the sequence switches 100, 200 andl 300 are not shown in their actual relative positions, but

' are arranged in such a manner as to simplifyy the circuits. The contacts within the lower rectangle iiiclosed in dotted lines on Fig. Y 1 are individual to the sequence' switch 200, those in the upper rectangle being individual to the sequence switch 300,-

while the remaining sequence switch contacts of Fig. 1 are individual to the sequenc switch 100.

Referring to Fig. 3, an operators loop 5 is shown, having serially includedthei'ein ringing keys 6 and' 7 and a coin return key 8. The operators set (not shown) is bridged across said loop by means of conductors 9.

In order to associate the operators loop 5 with any one of a plurality of cord circuits, a number of selectin switches, S, Sl and "S2, are provided. gEach of these switches is of the general type disclosed in the patents to McBerty or Reynolds, above referred to. Switches S1 and S2 are group switches, each having access to a group of cord circuits and being adapted to select a particular cord circuit in a group. In accordance with the arrangement*illustrated, the cord circuits, eight in number, would be arranged in groups of four each, the switch S1 having access to cords 1, 2, 3 and 1 and the switch S2 having access to cords 5, 6, 7 and 8, the cord circuit illustrated in Fig. 1 being cord No. 5. It will be understood, however, that as many cord circuits may be included in a group as may be found desirable, and that in practice a larger number of groups may be provided, each of which will have a switch such as S1 or S2 associated therewith, two switches only having been illustrated in order to simplify the diagram.

TheVV switch S is similar in construction to switches S1 and S2, but is common to all of the groups and is adaptedto associate the operators loop with the, terminals of any one of the group switches, such as `S1 or` S2.

When a cord circuit istakenjrfor use, the common switch VS, and the group switch associated with the group of that' particu-V lar cord, rotate simultaneously until the group switch finds the cord, and mon switch iinds the group switch. Normally, the two sections 1 and 2, of cord No. 5 are connected by means of a loop 10, 11,

said cord has been selected by the switch S'.

the. com- A through the contacts ofV switch S2. "When however, said loop is opened at the upperv contacts of the switch, and a new loop, consisting of conductors 12, '18 and 14 inter r is introduced therein. In a similar manner,

upon the'selection of any other cord circuit,

the opcrators loop will bejintroduced in the two sections of the cord circuit by means of vthe commonV switch and the proper group switch.

The contacts of the switches S, S1 and `S2 are so arranged, that before any loop Ais openedrthe loop to be introduced therein is connected thereto so'as to avoid clicks in the subscribers instrument, in other words, the contacts of the sequence switches which control the loops are of the make before break type- The invention may now be understood from a description of the operation in connection with cord No. 5, it being understood that the operation withrespect to other cords not shown is similar.

Listening n upon answering a call.

Assuming that cord No. 5 is to be used in answering a call, plug P is inserted in the answering jack, thereby energizing the sleeve relay 15. A lcircuit is then closed over the left-hand front contact of relay 15 from ground, lowerv sequence switch contact 101, left-hand front contact of relay 15, point 16, conductor 17, upper right-hand contact 18 of switch S2, through the winding of the'inotor magnet of the switch S*2 to battery. The motor magnet of theV switch S2 is energized over the above circuit, and the switch rotates from whatever position it may have been in at that time to its second position, whereupon the circuit above described is opened at contact 18, and the switch comes to rest. At the Sametime that the circuit above described was closed, a circuit was completed through the winding of the motor magnet of the switch S from battery over the upper contact 19 of said switch, conductor 20, point 21, upper .sequence switch contact 102, right-hand front isc switch S to ground. The winding of the motor magnet of switch AS is energizedover v contact of relayA 15,'cohductor 21to point 22, from which point the circuit continues to: ground overthe upper contact 23 of switch S2 if said switch is not in position 2.` `Ifsaid switchisalready in position 2, *the circuit will continue from point221over upper Ycontact 24 of switch S2, over conductor 26 and-over lower contact 27 of the` circuit above traced, and said switch is rotated from the pened to be at that time to vits fourth position, in which position the circuit above described is opened at contacts 19 and 27 and the switch comes to rest.

Upon switch S2 coming to rest in its second position, the loop 10, 11, which is closed over upper contacts 28 and 29, of `switch S2 in all positions except position 2, is ,opened at saidV contacts, and conductors 10 are extended over lower contacts 28 and 29 in thesame position, over conductors 12, over upper contacts 30 and 31 of switch S, conductors 14, upper contacts 32 and 33 of switchy S2 and conductors 13 to conductors l1. So long as the switch S is in any other position than position 4, the loop just described remains closed over contacts 30 and 3l. Upon switch S coming into its fourth position, however, the said loop is opened `and conductors 12 are extended over lower contacts 30 and 31, over the loop 5, lower contacts 34 and 35 of .switch S and over conductors 36 to conductors 14. Vith switch S2 in position-2 and switch S in position 4, it will be seen that the operators loop 5 is introduced in cord No. 5, over a circuit extending from section 1, over conductors 10, Ylower contacts 28 and 29-of switch S2, conductors 12, lower contacts 30 and 31 of switch Scoin control key `8, ringing keys 7 and 6',v loop 5, lower contacts 3 4 and 35 of switch S, conductors 36, conductors 14, upper contacts 32 and 33 of switch S2, conductors 13, and over conductors 11 to section 2. The operators set is now bridged across the cord circuit over conductor-s 9, and if the operator actuates any of the keys 6, 7 or 8, the ringing or coin-collect current, as the case may be, is applied to the answer ing end of the circuit only, the calling end being disconnected from the answering vend by thecontacts of the actuated kevs.

It will be noted that the windings of relays 37, 38 and 39 are arranged in parallel with the windings of the motor magnets of the switches S, S1 and- S2, consequently dur-V ing the time that the windings ofthe motor magnets of switches S and S2 were energized to complete the operations above described,relays 37 and39 were also energized.

Upon the .switches S and S2v coming to rest, however, relays 37 and 39 are `deenergized, thereby completing a circuit from ground position in which it hapover the back contact of relay 37, conductor 40, back contact of relay 38, conductor 41, back contact of relay 39, conductor 42, over lower contact 43 of switch S, conductor 44,

`contact 45 of switch S2, conducto-r 46, up-

per sequence switch contact 103, through `the winding of the motor magnet of se- `cluence switch 100 to battery.

sequence switch contact 201 and through the winding of the driving magnet of finder sequence switch 200 `to battery. Sequence switch 200 is driven into position 2, thereby completing a circuit from ground over the back contact of relay 48, upper sequence rswitch `contact 202, and through the winding of the finder switch The motor magnet of the of the driving magnet F to battery.

Ender -switch F is now `energized to drive finder wipers 49, 50, 51 and 52 over their waiting contacts until the wiper 51 rests upon the test contact 55 corresponding to cord No. 5, whereupon a circuit 1s completed from ground over the back righthand Contact of relay 47 upper sequence switch contact 105, contact 55, wiper 51, upper sequence switch contact 203, and through the winding of test relay 48 to battery.

Test relay-48 is energized over this circuit,

thereby opening the driving circuit ofthe finder switch F, so that the same com es to rest with its wipers-associated with the contacts corresponding to cord No. 5.

Relay 48 at its front contact completes a circuit from ground over sequence switch contact 204 and through the winding of the driving magnet of sequence switch 200 to battery, thereby driving the sequence switch 200 to position 5. As said sequence switch passed from position 3 to position 4, a new circuit is completed for test relay 48 from ground :over the back right-hand contact of relay 47, sequence switch contact 106, contact56and wiper 52 of thender F, sequence switch contact 301, winding of relay 57 ,-lowfer sequence switch contact 203, wind-` ing of test relay 48 to battery. Relay 57 is energized over the circuit above traced, and at its left-.hand front contact completes a locking circuit'for relays 57 and 48 independent of sequence switch contact 301. Re lay 57 `at`its front right-handcontact completes a circuit from groundover upper sequence switch contact 302, and through the Vwinding of the driving magnet of sender sequence switch 300 to battery. Sequence switch 300 isthereby driven into position 2.

The operator having now ascertained by means of her-listening set the number of the desired Subsc-wer, proceeds to set up the call upon her sending apparatus (not shown), thereby operating a key The sending apparatus above referred to forms no part of the present invention and is, therefore, not illustrated. This sending apparatus may beof any .well known type such of sequence switch 300 to battery, thereby dniving the sender sequence switch 300 into its third position. 1n this position a sending apparatus, conventionally represented by relays 59 and 60, isassociated with the cord circuit, the circuit of the sending appar-atus being as follows :#from ground, se-

quence switch contact 107, contact 58 andl wiper 49 of finder F, sequence savitch contact 304, Winding of relay 59, back contact of relay .60, wiper 50 and contact 54 of the finder- F, lower sequence switch contact 108, winding of relay 61, lower sequence switch contact 109 to battery. Relay 61 is energized over the circuit above traced, completingV atV its front contacta circuit from ground back contact of relay 47, front contact of relay 61, upper sequence switch contact 110 and through the winding of sequence switch 100 to battery. Sequence switch 1'00 is driven to its third position over the circuit above traced,'and in said posi-tion the selecting switch (not shown) associated with circuit 3 is driven through its group selecting travel under the control of the sender. After the last impulse has been transmitted by the sender the relay 60 is energized to open the circuit traced through the relay 61, which is thereby deenergized and at its back contact completes a. circuit from ground over' the back contact of relay 47, back contact of relay 61, lower sequence switchcontact 110, and through the winding of the motor magnet of sequence switch 100 to battery. Sequence switch 100 is now driven into position 4, in which the trunk limiting operation of the selector switchtakes place. At the completion of the trunk hunting operation the sequence switch 100 is driven to the sixth position, over a circuit not shown, since the details of the sending operations form no part of the present invention. In position 6 of sequence switch 100, the sending apparatus, comprising relays 59 and 60, is disconnected from 'the relay 61 and connected over upper sequence switch Contact 108 and 117 in position 6 to the circuit 3.v The remainder of the sending and selecting `operations now takes place in the sixth position of sequence switch 100, and need not be further described.

- Listening out after thecaltia set up on; the

senden n As soonas the operator liasset upthe call upon the sender, which it will Ibe reinemmoving out of position 2, she may disconnect lier set from the cord circuit while the sending and selecting operationsabove described are taking place. For this purpose she may depress the listening out key 62 (see Fig) I thereby completing` a circuit for relay 63,

which at its left-hand front contact corn'- pletes a locking circuit from ground over lower contact 64 of switch S, front left-hand contact of relay 63 and through `the winding of said relay to battery. Relay 63 'at its front right-hand contact completes a circuit from ground over contact 65 of' switch S and through the winding of the driving magnet of said switch to battery, thereby driving said switch to its twelfth position,

whereupon the locking circuit `of relay 6 3 1s opened at contact 64 and the switch comes to rest. In its twelfth position switch S is disconnected fro-niV all of the group switches, and consequently tlie operators the group switches.

shown. If it were desired to' have a greater munter of groups the same may be done by arranging the switch S with extra positions,

always, `of course, reserving one eXtra posi- The operator may also listen outl from the i particular cord, suoli as cord No.5, with which her set is associated, by plugging in with another cord, thereby shifting either the switch S or switch S2, or both, tothe proper positions to associate the loop 5 with the cord just plugged in. This `operation necessarily results in the disconnection of the operators loop5 from co-rd No. 5, as it .will Ibe noted that said loop can onlyV be connected to the cord'with. switch S in position 4 and switch S2 in position 2.A

Listening n t0 supervise a connection;

Should the operator desire to listen in upon a connection eitherestablished or pariio` tially established for supervisory purposes, 'j

she may `do so by depressing a listening key individual to the cord circuit used in establishing that particular connection. As-

suming that the operator desires to listen in I upon cord No. 5, she may depress thelistening key 66, thereby applying ground to conductors 17 and 20, so that the energizing circuits of the motor magnets of switches S and S2 are completed to drive said switches into positions 4 and 2, respectively', as detion in which the switch will not be associ- 100rv Vated with yany group switch.

scribed under the heading Listening vin upon answering a callf. In t'hese positions the operators loop 9fis introducedv in the a cord circuit. 1.

time to answer. other calls, `it is desirable that the sendershould be released from that cord in order notA to keep it'idle uselessly as would be the case if the sequence switch 100 of the cord were permitted to remain in position 2. Therefore, with switch 100 of cordv No. 5 in this position, should the operator listen out eitherby operating the listening out key 62, orbyplugging in with another cord, a ground willbemapplied to conductor 2l as' soon as switch S2 moves out of position 2 or switch Smoves out of position 4. A circuit will then be completed either from ground over upper contact 23 of switch' S2 to point 22, or from ground over lower contact 27 of "switchS and over conductor 26 and contact 24of switch S2 to point 22, from which point the circuit continues over conductor 21, front right-hand contact offrelay 15, lower sequence switch contact 102 now in position 2 andthrough the winding of relay 47 to battery. `Relay 47 is energized over the circuit` above traced, and at its middle front contact completes a'locking circuit over upper sequence switch contact 1,11'to ground, so that'it will remain locked up between positions 2 and 10, inclusive, of sequence switch 100.,- Relay 47 at its front right-hand contact completes `a circuit over sequence switch contact 112 and through the winding of the motor magnet of sequence switch 100, driving said switchfto position 4. In position 4 a circuit is completed from ground .1 over sequenceswitch contact 113,

lower sequence switoh'contact 104, winding or' relay 67 and" over the left-hand front contact of relay 47 to battery. ARelay `is therebyenergized and 'at'. its frontcontact completesv a circuitqfrom" ground over sequence switch contact f113, lower sequence switch contact 105 front contact of relay 67 Y lower sequencerA switch contact 103 and through the winding of the motor magnet 0f sequence switch 100 to battery. Sequence switch 100 is driven throughposition 5 `into position 6 under the control of its `master Vcontact 114. In position 6-the circuit of the driving magnet of sequence switch V100is completed over the' front right-hand Contact of relay 47 and sequenceswitchcontact 112, driving sequence switch 100-into position 7. In position 7 the circuit controlled by relay 67 drives sequence switch 100,1`nt0 position 100 passed out of vrighthand contact of relay 47 and sequence sequence switch A switch contact 112. As the l position 10, relay 47 was denergized, and in position 14 a circuit is completedfrom ground over the back righthand contact of relay 47, back contact of relay 61, lower sequence switch contact 110 and through the'windingof'the motor magnet of'sequence switch 100 to battery. The sequence switch is driven to position 17 over said circuit, and in position 17 relay 47 is energized over a circuit from ground, lower sequence 'switch contact 111 and Vthrough the winding of relay 47 to battery. Relay 47 `now completes the circuit previously' traced through the `winding of relay 67 which in turn at its front contact completes a circuitfrom ground over sequence switch contact 113, lower sequence switch contact 105, front contact of rela 67, lower sequence switch contact 103 andtirough the winding of the motor magnet of sequence switch 100 to battery. Sequence switch 100 is thereby driven Vfrom position 17 to position 18, in which position itremains. As soon as sequence switch 100 passed out of position 6, the leads from the sending apparatus extending over wipers 49l and 5 0 of the finder are disconnected from the circuit 3 at sequence switch contacts 108 and 117, thereby disconnecting the sender fromf the cord circuit. At the same time, the holding circuit of' relays 48 and 57 is opened at sequence switch contact 106, whereby relays 48 and 57 are deenen' glzed. Relay 48 at its back contact completes a circuit over lower sequence switch contact 202, through the winding of the motor" magnet or' the Vfinder sequence switch 200, thereby driving said vsequence switch through position 18 to position 1. Relay 57, upon being denergized, at.` its back right-ha`nd contact completes a circuit over lower sequence switch contact 302, through the wind-` ing of the driving magnetofthe sender sequence switch V300 thereby I driving said switch through position 18 to position 1. The sender is thereby restored to normal, and although the nder F is permitted to remain kwith its wipers resting upon the contacts individual to cord No. 5, `it is disconnected from said cord by reason of the opening of sequence switch contacts 108 and 117.

am 'amompleted connecllz'stem'ng in, upon tion.

Vmay set up a call.

.contacts individual from such other lcord circuit, it is desirable when the operator returns to said connection that a sender be picked up again in order that the operator Assuming then that the sender illustrated in Fig. 1, with its finder F and finder sequence switch 2001 is a second tact of.'relay-'37,conductor 40, back contact of relay 38, conductor 41, back contact of relay4 39, conductor 42, lower contact 43 of Switchs, conductor 44, upper contact 45 of switch S2, conductor 46, upper sequence switch contact 103, and through the winding of the motormagnet of sequence switch 100 to battery. Sequence switch 1003is1thereby driven from position 18 and through position 1 into position 2, so that the listening set is again connected to the cord circuit, and a sender associated vtherewith in the manner already set forth.

Restoring t partially completed connection.

If at any time Abetween the connection of a sender to the cord circuit-and the completion of the operation of setting up a connection by the sender, the operator desires to restore -the apparatus to normal in order to set up thev connection anew, she may depress the master restoring key 68, wherebyacireuit is completed from ground over the Contact of said key, contact 69 of the` switch S., conductor 70, contact .71 of switch S2, conductor 72, sequence switch contact 115, (which mayjbe in any position between positions 2 and 6, inclusive), and through the winding of relay 47 to battery.'Y The relay 47 is energized over this circuit and flocked up over sequence switch contact 111. The relay 47 upon being energized, drives the sequence switch 100 into position 18, as described un-- der the heading Listening out before setting up a connection. In position 18, since the operators set is at this time connected to the cord, a circuit is completed from ground over the back `Contact of relay 37, conductor 40, back contact of relay 38, conductor 41, back contact of relay 39, conductor 42, contact 43 of switch S in position 4, conductor 44, contact 45 of switch S2 in position 2, conductor 46, upper sequence switch contact 103 in position 18 and through the winding of the motor magnet of sequence switch 10() to battery. The sequence switch 100 is driven from position 18 through position 1 into po sition 2. As said sequence switch passed out of position 6 on its way to position 18, the

contact 115 is open in all other positions.

sender was released in thef manner already described. 1n position 2a senderis again i associated with the cord, as described u nder the heading Listening in upon answering `a call, and the apparatus is .againfready for setting up the call anew. The restoring key 68 is only effective from positions 'p2 to 6 of the sequence switch .100, as sequence switch After the sequenceV switch 100 has passed 'out of position 6, the connection to a called subscriber has been completed, and if the connection is wrong it' may b erestored asV described under the following heading. W z'trdmwz'ng the plug toA take down-acm- 80 z motion, f

Ii' the operator desires.: to take down an established connection sh e will first listen out by depressing the listening `out key 62 if her operators set happens tobe connected to the cord', and will then withdraw the plug of the cord from the answering jack. -Upon withdrawing vthe, plug the relay 15.i is `deenergized and a circuit is closed from conductor 21", which isalways grounded when the operators 'set is unconnected to the cord circuit, over the back right-hand ycontact of relay 15 and overthe uppernsequenc'e switch contact 116, if the connection taken down-has been-completely established, and thence through the winding of the motor magnet of sequence switch 100. The sequence switch is driven under the oint Y' i. control of its contacts 116 and 114 through 100 position 10 to'position 14. `In position 14 a circuit is closed fromground over Vsequence switch contact 113, back .contactof relay 61, lower 1 sequence vswitch vcontact V110, and through the winding of the motor magnet of sequence switch. 100 to-batter thereby-driving the sedience switch throughposition 15 to position 1 In position V17 relay 47 is energized 1in a manner already described, thereby completing. the circuit-of relay 67 which in turn "completes a circuit. for the motori magnet ofsequenceswitch 100 in a'nianner -alreadyl described .to vcliiveftlieV lsequence switch into position. 18. vIn position 18 the circuit of the motor magnet, of sequence switch 100 is.. again completed fromV the grounded conductor 21V over the back righthand contact of relay 15 and upper sequence switch contact 116, asv already .describechv thereby driving the sequence switch 100 into 120 position 1; Thev apparatus associated rwith the cord circuit is now Arestored tol normal.V Had vthe sequence switch 10QA been in any v position between positions 2 to .6, inclusive,

as would be the case with a-partially, established connection, upon withdrawing f the. plug from the jack a 4circuit would have been completed from grounded conductor21 over the back right-hand contact of relay 15, lower sequence switch contact 116V through 130 47 would be lockedup yfrom positions 2 to 10, thereby "operating to close circuits for the motor magnet-of sequence-switch 100 to drive said sequence switch to position 14 in the 4manner described under the Vheading Listening out before setting up connection. From position 14 the sequence switch 10() is driven through position 18 toy position 1 in the manner just described. i v

Wz'tLcZmQ/)z'ng a plug without releasing the t, commotion.`

If while listening in on a cord circuit the operator removes the plug from the jack, relay 15 is, of course, denergized, but no circuit changes result because the conductor 21 is ungrounded while the operator is listeni in. This .permits the operator to withdraw the plug "to either insert itin another jack, or for any other purpose without disturbing the existing connections.

-In accordance with this invention a very simple and yet eicient means has been devised whereby automatic listening in is Veffected without appreciable loss of time, and

while the Vinvention is disclosed as embodied in a particular form, it will be'understood that it is capable of variation in its embodiment without departingfrom the spirit of the invention as deiined in the appended claims.

What is claimed is:

1. In combination, a cord circuit, an operators loop including controlling keys serially connected therein and an operators set associated therewith, and means for introducing said loop in said cord circuit.

2. In combination, a group of cord circuits, an operators loop including controlling `keys serially connected therein and an operators set associated` therewith, and means for introducing said loop in any cord circuit of the group.

8. In combination, a cord circuit, an operators loop having ringing and coin control Akeys serially included therein, an operators set bridged across said loop, and means for introducing said loop in the cord circuit.

4. In combination, a group of cord circuits, an operators loop havin ringing and coin control keys serially inclut ed-therein, an operators set bridged across said loop, and means for introducing said loop in any cord circuit of the group whereby the ringing and coin control keys will be serially included in the cord circuit.

5. In combination, a plurality of transmission circuits, each transmission circuit being divided into sections, an automatic switch having a plurality of contacts, said switch being so arranged, that the sections of a plurality of transmission circuits may be simultaneously connected over its contacts.

A L 6. In combination, a plurality of cord circuits each divided into sections, an automatic switch having separate sets of contacts corresponding to each cord circuit, the sections of a cord circuit being vconnected to the i corresponding set of contacts, and means for individually controlling each set of contacts.

7 kIn combination, a plurality of cord circuits each divided into sections, a switching apparatus having contacts for individually connecting the sections of plurality of cord circuits, a loop, and means controlled by said switching` apparatus for including said loop between the sections of any cord circuit.

8. In combination, a plurality of cord circuits divided into groups, av loop, group switches for selecting any cord circuit of a group and for connecting said loop in said cord circuit.

9. In combination, a plurality of cord circuits divided into groups, a loop corresponding to each group, group switches for selecting a cord circuit in a group and connecting a loop therein, an operators loop, and a common switch for selecting a group and including the operators loop in the loop corresponding to that group.

10. In combination, a plurality of cord circuits divided into groups and each cord circuit consisting of at least two sections, a loop corresponding to each group, group switches for connecting a loop between. the sections of one cord circuit of each group and for directly connecting the sections of the remaining cord circuits of each group, an operators loop, and a common switch for introducing the operators loop in the loop corresponding to any group.

11. In combination, a plurality of cord circuits divided into groups and each cord circuit consisting of at least two sections, a loop consisting of atleast two sections corresponding to each group, group switches for connecting the loop of each group between the sections of one cord circuit of each group, and for directly connecting the sections of the other cords of each group, an operators loop, and a common switch for connecting said operators loop between the sections of a loop corresponding to one group, and for directly connecting the sections of the loops corresponding to the other groups.

12. In combination, a plurality of cord circuits divided into groups and each cord circuit consisting of at least two sections, a loop consisting of at least two sections corresponding to each grou-p, group switches comprising sets of make-break contacts for directly connecting the sections of the cord circuits of each group and for disconnecting the sections of any cord circuit in a group and connecting the loop of that group to said sections before the sections are disconnected, an operators loop, and a common switch comprising sets of make-break contacts for directly connecting` the sections of the loops l corresponding to the Various groups, and for circuits each consisting of at least two sec* tions, a loop, and a switch comprising sets of make-break contacts Jfor directly connecting the sections of the cord circuits, and for disconnecting the sections of one cord circuit Copies of this patent may be obtained for f and connecting said loop to said sections before they are disconnected.

In testimony whereof` Ihav'e signed my naine to this specification in the presence of l5 two subscribing `Witnesses, this eleventh day of October, 1917. i v

WILLIAM G. BLAUVELT.

Witnesses: i i

J. W. WALTERS, E. D. TALBOT.

ve cents each, by addressing the Commissioner of Patents, Washington, DIC. 

